Which combination has a maximum average triangle closure of 5 arcseconds?

• A. First order
• B. Second order, Class I
• C. Third order, Class II
• D. Third order, Class I

Answer: (C)

Understanding triangle closure helps you see how measurement quality and network design affect how well a triangulation closes on itself. Triangle closure is the residual you get when you complete a triangle from three survey points; smaller average closures mean better geometry and more precise observations.

As you use a higher-order network, triangles become smaller and the geometry improves, and when you pair that with a higher-precision data class, the expected average closure tightens further. This combination—third order with Class II—aligns with a scenario where you can keep the maximum average triangle closure around 5 arcseconds. The other options involve coarser networks or lower precision, which would typically yield larger average closures, not as small as 5 arcseconds.

So, the choice of third order, Class II is the one that matches a maximum average triangle closure of 5 arcseconds.